The invention relates to firearms of the type provided with a barrel, a cartridge chamber normally disposed behind the barrel, and a cartridge firing means acting on the rear end of the cartridge to be fired. The invention also relates to cartridges suitable for use in such firearms.
Some types of firearms such as sub-machine guns employ a so-called mass breech block, i.e. a breech block which ideally remains closed solely by reason of its mass without the intervention of any locking mechanism until the projectile has left the barrel. In such known types of breech blocks, however, a slight premature opening movement of the breech inevitably occurs, which opening must be kept as small as possible (for high efficiency of fire power) by selecting a relatively large mass for the block. Since, on the one hand, the block mass should be as large as possible for efficiency purposes, and on the other hand, the largest practical mass is determined by the overall weight considerations for the piece, the overall resulting design of the weapon is deleteriously effected.
In another type of non-locking firearm, the cartridges to be fired are inserted into recesses in a drum or barrel, after which they are brought successively by the turning of the drum into the firing position. In such revolver-type pieces, the weight of the breech (i.e. the drum) is, like the sub-machine gun indicated above, also disproportionately great compared with the remainder of the firearm. Additionally, in both designs, it is difficult to ensure effective sealing between the rear end of the barrel and the front end of the cartridge in the firing position, so that a significant portion of the force of the expanding gases from the explosion are wasted.